The present invention relates to implantable stimulation devices, e.g., cochlear prothesis used to electrically stimulate the auditory nerve, and more particularly to an implantable receiver and corresponding external (not-implanted) transmitter, inductively coupled with the implantable receiver, and a set of special tools, or a tool kit, that facilitates a method of implanting the implantable receiver so that it may be properly aligned with the external transmitter without the use of magnets in either the implantable receiver or external transmitter.
Cochlear stimulation systems are known in the art. Such systems are used to help the profoundly deaf (those whose inner ear is dysfunctional, but whose auditory nerve remains at least partially intact) to hear. The sensation of hearing is achieved by directly exciting the auditory nerve with controlled impulses of electrical current, which impulses are generated as a function of perceived audio sounds. The audio sounds are picked up by a microphone carried externally (not implanted) by the deaf person and converted to electrical signals. The electrical signals, in turn, are processed and conditioned by an external speech processor in an appropriate manner, e.g., converted to a sequence of pulses of varying width and/or amplitude, and then transmitted to an implanted receiver circuit. The implanted receiver circuit is connected to an implanted electrode array that has been inserted into the cochlea of the inner ear. Electrical current is applied to individual electrode pairs of the electrode array by the implanted receiver circuit as a function of the processed signal it receives from the external speech processor (which in turn is based on the audio sounds picked up the external microphone). It is this electrical current which directly stimulates the auditory nerve and provides the user with the sensation of hearing.
A typical cochlear stimulation system as is known in the art includes an external (not implanted) speech processor connected to a headpiece via a cable. A microphone is typically mounted to, or made an integral part of, the headpiece. Audio sounds sensed by the microphone are converted to corresponding audio signals which are sent to the speech processor. These signals are processed by the speech processor in accordance with a selected speech processing strategy. The processed signals are then sent back to the headpiece to one or more coils which inductively couple these signals to corresponding coils in an implanted receiver. The implanted receiver may also be referred to as an implanted cochlear stimulator (ICS). The ICS is integrally connected to a cochlear electrode array which is inserted into the snail-shaped cochlea of the inner ear of the user using known surgical techniques and tools. The electrode array includes a plurality of individual electrodes which are paired in an appropriate manner for electrical stimulation of the cochlea.
In order for the signals to be efficiently coupled from the external headpiece to the ICS through the inductive link created by the external and implanted coils, it is necessary for the headpiece coil to be properly aligned with the implanted coil. Heretofore, such alignment has been achieved by placing a magnet in the headpiece that aligns the headpiece with a corresponding magnet in the ICS. Such magnet also holds the headpiece in place on the head of the user. See, e.g., U.S. Pat. No. Re. 32,947.
For some users, the headpiece is easily hidden under a nice crop of hair or attractive clothing or head gear. For other users, however, the headpiece cannot be easily hidden, leaving such users very conscious and ill-at-ease in wearing the headpiece. Improvements are needed, therefore, in the way that alignment is achieved between the headpiece and implanted receiver that allow all users to easily and comfortably wear the headpiece without being self-conscious of its presence.
Regardless of the type of implant involved (i.e., regardless of whether the implant is part of a cochlear stimulation system or some other device, e.g., a neural stimulator), the magnet used in prior art implanted receivers (to achieve and maintain proper alignment between the external and implanted coils) prevents, or is very detrimental to the effective use of, magnetic resonance imaging (MRI) techniques in the vicinity of the implanted magnet (which would typically include, for a cochlear stimulation system, the entire head region). Because MRI is an extremely valuable medical diagnostic tool (used by medical personnel to identify, locate, and treat a myriad of problems which could arise in any patient), deaf or other patients who are candidates for implantable stimulation systems would very much like the option of being able to use MRI, should the need arise for such use. Hence, there is a need in the art for other ways--ways which do not involve the use of an implanted magnet--to achieve the needed alignment between the external and implant coils.